On the WebTutor.pl site they've posted the second part of their series looking at the benchmark results from their tests running HipHop. You can find their first post with some of the introductory setup and information here.

In previous article I measured the performance of HipHop for PHP by performing some tests downloaded from the shootout.alioth.debian.org website. Unfortunately the test list was incomplete. Only six tests were selected to avoid potential incompatibility issues with the HipHop compiler.

In this new post he provides the results for two more tests: regex-dna and k-nucleotide. He outlines the testing platform and shares the results of testing some pretty basic scripts. His results were interesting and found that some operations the HipHop compiler actually slowed down.